Begley

Hi, We have recently had our first babies hatched. One died and the other doesn't fly. His name is Worzel and he has been out of the nesting box for 2 weeks. He is very small and today i was told he has French Moult. I was told to take him out of the aviary and keep him separate from other budgies as he is contagious. After reading the Q&A I am wondering if it is safe to put him back with his parents? Other than treating for mites is there anything else he needs to treat this. And we live in New Zealand, so it is here.